The present invention relates to a laser scan microscope which irradiates a sample with a laser beam while scanning the laser beam over the sample, detects the light beam transmitted through the sample by means of a detector to obtain an image of the sample, and observes the obtained image.
A laser scan microscope has a laser scanning observation optical system which scans a laser beam over a sample (focal surface), and detects the beam transmitted through the sample by use of a detector. The laser scan microscope may have an ordinary observation optical system in which an image of the sample is observed with the naked eye (the observer) or another method, in addition to the laser scanning observation optical system.
The laser scan microscope having both the above optical systems is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-155505. The microscope disclosed in this Publication has a mechanism using an optical path-switching reflecting mirror for selectively switching the optical path of the laser scanning observation optical system and the optical path of the ordinary observation optical system.
More specifically, when the laser scanning observation optical system is used, a laser beam emitted from a light source is transmitted through the sample, and guided to a condenser lens. The laser beam transmitted through the condenser lens is deflected by the optical path switching mirror, transmitted through a pupil relay lens unit (for the transmitted beam through the sample), and reaches the detector. Image processing is carried out on the basis of light intensity distribution detected by the detector, and the processed image is displayed on a monitor.
On the other hand, when the ordinary observation optical system is used, the optical path-switching reflecting mirror is retreated from an optical path. Thus, the light radiated from the illumination lamp, which serves as a light source of the ordinary observation optical system, is not reflected by the reflecting mirror, but travels along the same optical path as in the laser scanning observation optical system in the reverse direction to the beam traveling in the case of using the laser scanning observation optical system. Therefore, the light is transmitted through the condenser lens, and illuminates the sample. The light transmitted through the sample is introduced to an eyepiece, as a result of which an image of the sample is observed with the naked eye through the eyepiece.
Since the above conventional microscope has a structure wherein an image of a pupil of the condenser lens is projected onto the detector, if the accuracy with which the reflecting mirror reflects the transmitted beam is low, the beam inclines with respect to the detector when it is incident thereon. Consequently, there is a case where the intensity of the beam is not accurately detected, and thus an obtained image has unevenness. In order to solve this problem, it is necessary to provide a mechanism for driving the reflecting mirror to retreat it with high accuracy, thus increasing the size of the microscope.
Moreover, in the laser scanning observation optical system, if condenser lens units having different pupil positions are provided, it is necessary to provide pupil relay lens units respectively associated with the condenser lens units. Thus, each time one of the condenser lenses is exchanged for the other, one of the pupil relay lens units must also be exchanged for the other. Although exchanging of the pupil relay lens units does not adversely affect observation using the ordinary observation optical system, the apparatus is complicated and enlarged anyway.